I'm under the impression that Reg B's Right to Receive Appraisal Notice only pertains to 1-4 unit properties. Is this true? I don't need to issue one for commercial properties? While the borrower pays for the commercial appraisal, it is out of courtesy that we provide a copy of the report. But it's not mandated, right?

You are correct that it only applies to 1-4 dwellings. However, just a FYI, rental houses are not "commercial properties" for the purpose of the regulation. (I have had this agument with lenders in the past. )

Here's the definition of a dwelling from 202.14;

(c) Definitions. For purposes of paragraph (a) of this section, the term dwelling means a residential structure that contains one to four units whether or not that structure is attached to real property. The term includes, but is not limited to, an individual condominium or cooperative unit, and a mobile or other manufactured home. The term appraisal report means the document(s) relied upon by a creditor in evaluating the value of the dwelling.

What about a mixed use property where there is commercial space on the ground floor and two apartments above?